Organometallics 1984,3, 327-329
327
Table I. Rate Constants for the Exchange Reaction of 0.1 M (p-Xy1ene)tricarbonylchromiumwith Benzene at 1 7 0 "C in Benzene Containing (Hexamethylbenzenehricarbonvlchromiuma concn of HMBCr(CO),, M
107hobsd,8 - 1
b 12.4 i 9.5 i 7.5 k 6.8 i 4.0 t
0.3 1.3 1.0 0.7 0.9 2.0 + 0.1
0.18 0.155 0.12 0.08 0.055 0.00
e
d
C
11.5 k 0.3 8.8 * 0.3 8.5 + 0.3 6.5 * 0.1 4.4 i 0 . 3 1 . 8 i 0.1
12.9 * 9.7 i 10.0 t 7.2 f 4.4 i 2.0 k
1 2 . 1 t 0.5 9.7 i 1.2 8.2 f 1.3 6.7 i 0.7 4.4 + 0 . 6 1 . 8 i 0.1
0.8 0.6 0.5 0.4 0.2
0.1
Cyclohexane was employed as internal standard. Obtained from disappearance of p-xylene complex CH, protons. Obtained from appearance of (benzene)tricarbonylchromium. Obtained from disappearance of p-xylene complex ArH protons. e Obtained from appearance of free CH, protons (p-xylene and hexamethylbenzene). a
nisms.' In this catalysis the lone pairs on the bound CO are proposed to function in the manner suggested for the catalysis of these reactions by ketones, ethers, and nitriles (eq i2).398
I
I
oc
/'\
1
c
co
0
The increase of kII in the order benzene complex < toluene complex < HMB complex accords with this proposal. It seems likely that such metal carbonyl catalysis is a general phenomenon.
Figure 2. Plot of kobd vs. concentration of (hexamethylbenzene)tricarbonylchromium for arene exchange between (pxy1ene)tricarbonylchromium and benzene in the presence of (hexamethy1benzene)tricarbonylchromiumat 170 O C : X (-), kow disappearance of @-~ylene)Cr(CO)~-CH~; 0 (---), k a appearance of (ben~ene)Cr(CO)~; * k o w disappearance of @xylene)-
ArM'(CO),
+
M-CO
[
Trl
M-CO-M'(CO),
e
Ar'M(CO),
(13)
Further details of catalyzed and uncatalyzed exchange reactions are discussed elsewhere.8
(e-),
Cr (C0)3-ArH.
tricarbonylchromium, affords a mean second-order rate constant of 5.5 X lo4 M-' s-l for the term - d[BZCr(CO),] dt k2[(p-xylene)Cr(CO),] [HMBCr (CO),] + ... (10) This value compares well with Strohmeier's values of kII = 1.5 X lo4 and 3 X lo4 M-l s-l for the second-order terms in eq 1 for Ar = benzene and toluene, respectively. We suggest a novel catalytic function of an (arene)tricarbonylchromium complex illustrated for our reaction shown in eq 11. Thus we have confirmed Strohmeier's
Acknowledgment. We are grateful to the National Science Foundation (Grant CHE 81-20969) for financial support of this research. Registry No. (p-Xylene)Cr(CO)3,12129-27-0; (hexamethylber~zene)Cr(CO)~,12082-08-5; (ben~ene)Cr(CO)~, 12082-08-5; benzene, 71-43-2. (7) We have shown that a labeled Cr(13C0)3group can be exchanged intact in the presence of l2C0, eliminating the mechanism of eq 4.8 (8) Traylor, T. G.; Stewart, K.; Goldberg, M., submitted for publication.
High-Yield Acyl Anion Trapping Reactions. Nucleophilic Acylation of Dlaikyl Disulfides, S-Alkyl Thloesters, and Elemental Sulfur Dletmar Seyferth" and Richard C. Hul Department of Chemistry Massachusetts Institute of Technology Cambridge, Massachusetts 02 139 Received December 13, 1983
Q oc
/c
I r\
C
co
0
kinetic studies but eliminated both the proposed mecha0276-733318412303-0327$01.50/0
Summary: Organic disulfides may be acylated to give S-alkyl thioesters in good yield by the RLi/CO in situ procedure at very low temperatures. Similar nucleophilic acylation, at -78 OC, of elemental sulfur, followed by addition of iodomethane, gives RC(0)SMe. 0 1984 American Chemical Societv
328 Organometallics, Vol. 3, No. 2, 1984
Communications
Scheme I
Table I. In Situ Nucleophilic Acylation of Disulfides and Elemental Sulfura
R'
RLi
sulfur compds
t-BuLi n-BuLiC t-BuLi sec-BuLi n-BuLi t-BuLi sec-BuLi n-BuLi t-BuLi n-BuLi
RLi/CO
/Me3SiCI /Me3SiCI
MeSSMe MeSSMe n-PrSSPr-n n -PrSSPr-n n -PrSSPr-n n -BuSSBu-n n - Bu SSBu -n n-BuSSBu-n i-PrSSPr-i i-PrSSPr-i
0 0
RC-CR'
It00 0It
t-BuLi n-BuLi
In previous communications we have described the nucleophilic acylation of aldehydes,l esters,lp2 lactones? and trialkyl~hlorosilanes~ by means of the in situ RLi/CO system at very low temperature (-110 "C -135 OC) (Scheme I). The nucleophilic cleavage of organic disulfides by ~ r g a n o l i t h i u m ~ (eq 1) and organo-
-
RLi
+ R'SSR'
-
RSR'
+ R'SLi
(1)
magne~ium~~,~v* reagents is well-known, and thus the nucleophilic acylation of organic disulfides seemed an interesting possibility (eq 2). If successful, such reactions would provide a new route, based on readily available starting materials, to S-alkyl thioesters. RLi/CO
+ R'SSR'
low
temperature
RC(=O)SR'
+ R'SLi (2)
We have found that the reaction shown in eq 2 is easily effected. In a typical example, a 500-mL three-necked flask equipped with a mechanical stirrer, a Claisen adapter (fitted with a low-temperature thermometer rtnd a gas outlet tube), and a no-air stopper which held a gas dispersion tube (which was connected to a carbon monoxide cylinder) was charged with 130 mL each of dry THF and diethyl ether, 40 mL of pentane, and 1.5 mL (9.55 mmol) of di-n-propyl disulfide. This solution was cooled to -110 OC, and carbon monoxide was bubbled in for 30 min. Then a solution of n-butyllithium (2.54 M in hexane, 3.70 mL, 9.4 mmol) was added a t a rate of 0.24 mL/min by means of a syringe pump (Orion &search, Inc., Model 341). After the addition had been completed, the now yellow reaction mixture was stirred at -110 OC under CO for 2 h and then was allowed to warm to room temperature while the CO stream was continued. After hydrolysis with saturated NH4C1solution, the organic layer was separated, dried, and concentrated (9-in. Vigreux column). GLC analysis of the (1) D. Seyferth, R. M. Weinstein, W.-L. Wang, and R. C. Hui, Tetrahedron Lett. 1983, 24, 4907. (2) D. Seyferth, R.M. Weinatein, and W.-L. W w ,J.Org. Chem., 48,
1144 (1983); (3) R.M. Weinstein, W.-L. Wang, and D. Seyferth, J. Org. Chem., 48, 3367 (1983). (4) D.Sevferth and R. M. Weinstein. J. Am. Chem. Soc.,. 104.. 5534 (1982). ( 5 ) (a) B. J. Wakefield, "The Chemistry of Organolithium Compounds";Pergamon Press: Oxford, 1974; pp 192, 214. (b) A. J. Parker and N. Kharasch, Chem. Rev., 59, 583 (1959). (c) L. Field in "OrganicChemistry of Sulfur", S. Oae, Ed., Plenum Press: New York, 1977; pp 356-7. (6) M. S. Kharasch and 0. Reinmuth, 'Grignard Reactions of Nonmetallic Substances"; Prentice-Hall: New York, 1954; p 1301.
Product (% vield)b t-BuC(0 ) S M e ( 6 6 ) n-BuC( 0 ) S M e ( 7 8 ) t-BuC(0)SPr-n ( 7 1) sec-BuC(0)SPr-n ( 7 4 ) n-BuC( 0)SPr-n ( 7 3 ) t-BuC(0)SBu-n ( 7 3 ) sec-BuC(0)SBu-n ( 7 6 ) n-BuC(0)SBu-n(81) t-BuC(0)SPr-i ( 5 5 ) n-BuC(0)SPr-i ( 6 3 )
(MeI)
t-BuC(O)S(CH,),SMe ( 6 3 )
(MeI)
n-BuC( O)S(CH,),SMe ( 5 5 )
t-BuLi
0
t-BuC(O)S(CH,),SMe ( 6 8 )
n-BuLi
0
n-BuC(O)S(CH,),SMe ( 6 2 )
(MeI) (MeI)
t-BuLi d , e s* (Me11 t-BuLie S8 (Me11 sec-BuLidSe S8 (Me11
t-BuC( 0 ) S M e ( 5 7 ) t-BuC( 0 ) S M e ( 4 5 ) sec-BuC(0 ) S M e ( 5 1 )
a Using the procedure given in the text unless otherwise noted, reactions were carried out by using 1:l RLi/ substrate stoichiometry at -110 "C. Yield based o n RLi charged. Reaction carried out at - 1 3 5 "C. Reaction carried out at -78 "C. e 1:2 RLi/S stoichiometry used.
residue showed the presence of S-n-propyl thiopentanoate, n-C4H9C(0)SC3H,-n,n20D1.4597, in 73% yielda7 The other reactions that were carried out are summarized in Table I. A reaction temperature of -110 "C was found to be satisfactory; use of lower temperatures usually gave lower product yields. Lower yields of thioesters were obtained also at -78 OC. In some reactions involving tertbutyllithium a 1,2-diketone, t-BuC(O)C(O)Bu-t, was a minor byproduct. This presumably was produced by the reaction of the t-BuLi/CO reagent with the thioester (eq 3). Confirmation of such a process was given by a reaction of CH3C(0)SC2H5with the t-BuLi/CO reagent at -110 OC (1:l t-BuLi/thioester stoichiometry) which gave Me3CC(O)C(O)Me in 67% yield. Me3CLi/CO
t Me3CC4" % Me3CC-CCMe3
II0 II0
S 'R
t LISR (3)
If the acyl halide corresponding to the acyllithium used is available, then the yield of the thioester can be effectively more than doubled. Equation 4 illustrates this in Me3CLi/C0
+
n-Bu2S2
-110 " C
Me3CSSBu-n t n - B u S L l
II0 room temp
U
the case of the t-BuLi/CO reagent. The yield of Me3CC(0)SBu-n obtained when pivaloyl chloride was added to the reaction mixture after it had warmed to room tem(7) This and all other new compounds have been fully characterized (always C and H and sometimes S analysis; IR and 'H NMR spectra).
Organometallics 1984, 3, 329-331
perature was 171% based on t-BuLi (or 85.5% based on both n-BUS units of the disulfide). Such nucleophilic acylations of cyclic disulfides are of special interest in that the mercaptide leaving group (cf. eq 2) is retained in the acylation product (eq 5). In such
"
n=4,5
RCS(CH2 ),,SMe ( 5 )
II
329
and characterized by X-ray diffraction. 1 is readily protonated by HBF, at the &carbon to yield an isolable pethylidyne salt, 2, which in turn is reduced by NaBH, to give the corresponding p-ethyliiene complex 3. Complex 3 is also formed on treatment of 1 with H, at 60 OC, but under these conditions competitive hydrogenolysis of 3 to ethane occurs. Reaction of 1 with CpMo(CO),(L)H (L = CO, PPh,) affords the mixed-metal cluster 4 in good yield, in a rational and potentially general route to p-carbyne trinuclear systems. Possible mechanisms are briefly discussed.
0
a reaction of the t-BuLi/CO reagent with 1,2-dithiane (n = 4) the methylated product Me3CC(0)S(CH2),SMe was obtained in 63% yield. Similar reactions are listed in Table I. In view of this facile nucleophilic acylation of organic disulfides, it was of interest to see if the acylation of elemental sulfur, cycZo-S8,also could be effected. (Elemental sulfur, it is known: reacts with alkyllithiums to give lithium alkyl mercaptides, RSLi.) Such a reaction does indeed occur (eq 6). The yield of thioester was lower (45%) when Me3CLiICO t Ss
--78 'C
M0I
- 5 0 'C
Me3CCSMe
II
0
57%
the reaction was carried out at -110 "C. In both reactions the l,Z-diketone, t-BuC(O)C(O)Bu-t, was a minor byproduct. The sec-BuLi/CO reagent reacted with elemental sulfur a t -78 "C, and after treatment of the reaction mixture with iodomethane the yield of sec-BuC(0)SMe was 51%. With n-butyllithium this chemistry was not successful in that at -78 "C the yield of n-BuC(0)SMe was only 5%, while the n-BuC(O)C(O)Bu-n yield was 32%. The provenance of the latter has not yet been established. Direct nucleophilic acylation with in situ generated acyllithium reagents thus seems to be a rather generally applicable procedure. As noted, we have been able to acylate aldehydes, ketones, esters, lactones, and trialkylchlorosilanes, and now, organic disulfides, thioesters, and elemental sulfur have been added to this list. Further work in progress is aimed at the in situ nucleophilic acylation of still other organic, organometallic and inorganic electrophiles.
Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, and to the National Science Foundation for support of this work.
Synthesis, Crystal and Molecular Structure, and Reactions of the Brldglng Vlnylldenedlcobalt Complex (p-CCH,)(CpCoCO),. Reaction with Molybdenum Hydrides To Give a Heteronuclear Cluster Complex Erlc N. Jacobsen and Robert G. Bergman' Department of Chemistry, University of California Berkeley, Californla 94 720 Received September 20, 1983
Summary: The first unsubstituted dicobalt p-vinylidene complex (p-CCH,)(CpCoCO), (1) has been synthesized 0276-7333 f 84f 2303-0329$01.50 f 0
As members of the important family of complexes containing a carbon bridging two or more metals, bridging vinylidene systems are particularly interesting in that the organic moiety is unsaturated. Therefore, in comparison with bridging allcylidene' and allcylidyne2complexes, they are expected to display unique reactivity at that site. Despite the fact that mono- and dinuclear vinylidene complexes of several transition-metal complexes are known,3 no simple cobalt vinylidene complex has yet been reported., In addition, aside from simple protonation reactions,3J0 the chemistry of bridging vinylidene complexes remains virtually unexplored. We describe here the synthesis of a new p-vinylidene system (1) by a route that exploits the versatile reactiviV6 of the radical anion [CpCo(C0)I2-, and the structural characterization of 1 by X-ray diffraction. Preliminary studies on the chemistry of 1 are also reported, including its reaction with mononuclear metal hydrides to afford a rational and potentially general route to p-carbyne trinuclear cluster systems. Addition of 1,l-dibromoethylene' to a stirred suspension of Na[CpCo(CO)I2at ambient temperature results in the appearance of new absorbances at 1796 (due to neutral dimer [C~CO(CO)]~) and at 1960 cm-' in the IR spectrum of the solution. Purification by chromatography on neutral alumina I1 under air-free conditions affords the deep red &-vinylidene)bis[ (~5-cyclopentadienyl)carbonylcobalt] (1)8 in 40% of the theoretical yield (Scheme I). Only a single, presumably trans isomer could be detected by NMR and (1)For reviews, see: (a) Her", W. A. Angew. Chem. 1982,94,llEi (b) Herrmann, W. A. Adu. Organomet. Chem. 1982,20,159. (2)For reviews, see: (a) Seyferth, D. Adu. Organomet. Chem. 1976, 14,97. (b) Dickson, R. S.; Fraaer, P. J. Ibid. 1974,12,323. (3)Dinuclear p-vinylidene complexes have been reported for the following metals. (a) MIX Folting, K.; HuRman, J. C.;Lewis, L. N.; Caulton, K. G. Inorg. Chem. 1979,18,3483: (b) Fe: Kao, S. C.; Lu, P. P. Y.; Pettit, R. Organometallics 1982,1,911. Dawkins, G. M.; Green, M.; Jeffery, J. C.; Sambale, C.; Stone, F. G. A. J. Chem. SOC.,Dalton Trans. 1983,499. (c) Ru: Davies, D. L.; Dyke, A. F.; Endesfelder, A,; Knox, S. A. R.; Naish, P. J.; Orpen, A. G.; Plaas, D.; Taylor, G. E.J. Organomet. Chem. 1980, C43. Cooke, M.; Davies, D. L.; Gherchais, J. E.; Knox, S. A. R.; Mead, K. A.; Roue, J.; Woodward, P. J. Chem. SOC.,Chem. Commun. 1981,862. (d) R h AI-Obaidi, Y. N.; Green, M.; White, N. D.; Taylor, G. E. J. Chem. SOC.,Dalton Trans. 1982,319. (e) Fe-Mn: Kolobova, N. E.;Ivanov, L. L.; Zhivanko, 0. S.; Aleksandrov, G. G.;Struchkov, Yu. T. J. Organomet. Chem. 1982,228,265. (4)To our knowledge the only cobalt complexes in the p-vinylidene class are the monohalo- and dihalo-substituted (fi-butenolido)(pvinylidene)hexacarbonyldicobalt complexes reported by: Horvath, I. T.; Palyi, G.;Marko, L.; Andreetti, G.D. Inorg. Chem. 1983,22,1049. (5)Schore, N. E.;Ilenda, C. S.; Bergman, R. G.J . Am. Chem. SOC. 1976,98,7436;1977,99,1781. (6)(a) White, M. A.; Bergman, R. G. J. Chem. SOC.,Chem. Commun. 1979,1056.Bergman,R.G. Acc. Chem. Res. 1980,13,113.(b)Theopold, K. H.; Bergman, R. G. J . Am. Chem. SOC.1980, 102, 5694; Organometallics 1982,1, 1571. (c) Theopold, K. H.; Bergman, R. G. J. Am. Chem. SOC.1983,105,464. (7)Prepared by addition of CHBr&H,Br to a suspension of K2C09 and KOAc in boiling ethanol. The dibromide is collected by distillation aa an azeotrope with ethanol at 90 OC. Verhulst, J.; van Hemelrijck, F.; Jungers, J. C. Natuurwet. Tijdschr. (Ghent) 1943,25,203.
0 1984 American Chemical Society
